Medjerda River

The Medjerda River (also known as the Wadi Majardah, Wadi Mejerha, Oued Majardah, and Bagradas) is a river in Algeria and Tunisia. With a length of 450 km, it is the longest river of Tunisia. It originates in northeastern Algeria and then flows eastwards to Tunisia, then entering the Gulf of Utica of the Mediterranean Sea.

Medjerda is Tunisia's crucial waterway providing water to the country's supply facilities; it is also vital to the people living near the river. Water from Medjerda is used for irrigation and is pivotal to the region's agriculture. It flows from northeast Algeria in the Atlas Mountains more than 460 kilometres (290 miles) through Tunisia before emptying in the Gulf of Tunis and Lake of Tunis. It is the most important and longest river in Tunisia and is dammed in several locations, being a major supplier of water to the country's wheat crops. A very strategic river in North Africa, it was fought over and settled many times in history by the Berbers, Phoenicians, Punics, Romans, Vandals, Byzantines, Arabs, and the Ottomans. Several major cities, such as Utica, Carthage, and eventually Tunis were founded on or in close proximity to it.

The Gulf of Utica was formed during the postglacial transgression about 6,000 years ago. Over time, fluvial deposits from the Medjerda gradually filled up the northern part of the gulf. The succession of events during historical times has been inferred from ancient documents and archaeological evidence. Besides morphological ground observations, aerial and satellite photographs have been used to analyze how the landscape has evolved over the past 3,000 years. The gulf's southern part was filled up in late ancient times. The sea gradually withdrew from the northern part during the Middle Ages and modern times. The Ghar el Melh lagoon is the last vestige of what used to be the Utica gulf. Following the last big flood in 1973, the Medjerda shifted its course once again. It now flows through a canal originally dug to evacuate the overflow of flood waters.